How To Install and Use Memcache on Ubuntu 12.04

About Memcache

Setup

sudo apt-get update

sudo apt-get install mysql-server php5-mysql php5 php5-memcache

Install Memcache

sudo apt-get install memcached

sudo apt-get install php-pear

sudo apt-get install build-essential

sudo pecl install memcache

echo "extension=memcache.so" | sudo tee /etc/php5/conf.d/memcache.ini

Confirm Memcache and See Stats

ps aux | grep memcache

 echo "stats settings" | nc localhost 11211

How Memcache Works

function get_foo(foo_id)
    foo = memcached_get("foo:" . foo_id)
    return foo if defined foo

    foo = fetch_foo_from_database(foo_id)
    memcached_set("foo:" . foo_id, foo)
    return foo
end

A Simple Memcache Example

use test;

grant all on test.* to test@localhost identified by 'testing123';

create table example (id int, name varchar(30));

insert into example values (1, "new_data");

exit;

nano memtest.php

• Start off by creating a new persistent connection with memcache, which runs on memcache’s default port, 11211.

  <?php
  $meminstance = new Memcache();
  $meminstance->pconnect('localhost', 11211);



• The next step is to connect to the new mysql database with the user that we created earlier:

  mysql_connect("localhost", "test", "testing123") or die(mysql_error());
  mysql_select_db("test") or die(mysql_error());



• After that, go ahead and create the query that we will pose to the server, as well as provide a key to identify that specific action:

  $query = "select id from example where name = 'new_data'";
  $querykey = "KEY" . md5($query);



• The script first searches the cache for the answer to the query. If the result does not exist, the script reroutes the question to the original database. Once the query has been answered by the original database, the script stores the result in memcache, using the "set” command-- which both saves it and allows the user to designate the number of seconds that it should remain in the cache (600 would save it in the cache for 10 minutes).
  
  When we run the script for the first time, it will inform us that the data was collected from the mysql database. However, as it does so, it stores the information in the cache, so that a second run of the script retrieves it from the cache and lets the user know.
  
  In 10 minutes the cache is emptied once more and running the script will make it access the database once again.
  
  

  $result = $meminstance->get($querykey);
  
  if (!$result) {
         $result = mysql_fetch_array(mysql_query("select id from example where name = 'new_data'")) or die('mysql error');
         $meminstance->set($querykey, $result, 0, 600);
  print "got result from mysql\n";
  return 0;
  }
  
  print "got result from memcached\n";
  return 0;
  
  ?>

<?php
$meminstance = new Memcache();
$meminstance->pconnect('localhost', 11211);

mysql_connect("localhost", "test", "testing123") or die(mysql_error());
mysql_select_db("test") or die(mysql_error());

$query = "select id from example where name = 'new_data'";
$querykey = "KEY" . md5($query);

$result = $meminstance->get($querykey);

if (!$result) {
   $result = mysql_fetch_array(mysql_query("select id from example where name = 'new_data'")) or die('mysql error');
   $meminstance->set($querykey, $result, 0, 600);
print "got result from mysql\n";
return 0;
}

print "got result from memcached\n";
return 0;

?>

# php memtest.php 
got result from mysql

# php memtest.php 
got result from memcached

# php memtest.php 
got result from memcached